Engine systems often comprise a cylinder block with an attached cylinder head that include a series of cylinders with surrounding material for attaching various components. Cylinder blocks and cylinder heads also include cooling systems that comprise a number of cooling passages that surround the cylinders. A coolant, such as water, oil, glycol, etc., may be pumped or otherwise sent through the cooling passages to remove heat from the cylinders and cylinder block and head via heat exchange. The cooling passages may include inlets and outlets such that coolant at a lower temperature is directed into the cylinder block and head while coolant at a higher temperature is exited from the cylinder block to a heat exchanger or other device. As such, the temperature of the cylinder block and cylinder head may be maintained within a desirable range during engine operation. In some systems, there may be fluidic communication between the cooling passages of the cylinder head and cylinder block. Various cooling systems exist for providing different amounts of cooling to different areas of the cylinder block.
In one approach to provide a cooling system to cool cylinders of an engine, shown by Lenz et al. in U.S. Pat. No. 8,555,825, cooling passages are provided in a cylinder head for receiving coolant from the cylinder block. In one embodiment, coolant is routed out of a cylinder block water jacket via a cooling passage of the cylinder head, along a bridge between two cylinders, and into another cooling passage of the cylinder head to provide cooling to portions proximate to intake and exhaust valves of the cylinders. In other words, coolant is pumped from the cylinder block to the cylinder head, then back into the cylinder block along the bridge in a cooling slot, and finally back into the cylinder head. The cooling slot provides the intermediate connection to allow coolant to flow from the cylinder block into the cylinder head. The fluidic communication between the cylinder head and cylinder block allows coolant located in the cylinder block to flow into the cylinder head proximate to the cylinder and intake/exhaust valves.
However, the inventors herein have identified potential issues with the approach of U.S. Pat. No. 8,555,825. First, while the cooling passages proposed by Lenz et al. allow fluidic communication between the cylinder block and cylinder head, only a single coolant may be routed through the cooling passages. The system does not allow a different degree of cooling to be provided by a different coolant in a particular area of the cylinder block/head assembly. For example, if one portion of the cylinders is desired to be maintained within a certain temperature range while another portion of the cylinders is desired to be maintained within a different temperature range, then two coolants may be directed throughout the assembly. Furthermore, coolant from the coolant jacket surrounding the cylinders may have a high temperature before entering the cooling slot in the bridges as well as the areas proximate to the intake/exhaust valves, thereby decreasing the efficiency of heat removal. Since coolant passing into the cylinder head may be heated by the cylinders first, then a lower amount of heat than desired may be removed from the bridge and cylinder head.
Thus in one example, the above issues may be at least partially addressed by a method, comprising: cooling a cylinder head with a first coolant; cooling a cylinder block with a second coolant, the second coolant a different liquid than the first coolant; and cooling a plurality of bore bridges with the first coolant while maintaining separation between the passages containing the first and second coolants, the plurality of bore bridges in between adjacent cylinders of the cylinder block. In this way, the cylinder head and cylinder block are cooled with separately-maintained cooling systems while a portion of the first coolant (e.g., water) of the cylinder head may aid in cooling certain portions of the cylinder block, in particular the bore bridges.
When a vehicle is first turned on, it may be desirable to rapidly increase the temperature of the engine in order to improve fuel economy. While a water-cooled cylinder block may most effectively remove heat from the engine, a more-than-desired amount of heat may be removed. Alternatively, an oil-cooled cylinder block may remove heat less rapidly than the water-cooled cylinder block, but localized high-temperature regions may exist that adversely affect engine performance. The regions may include the portions in between cylinders known as bore bridges. In some examples, the oil-cooled cylinder block with water-cooled bore bridges may allow the engine to rapidly warm-up while providing sufficient cooling to the bore bridges via the water passages with water from the cylinder head.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.